The present invention relates, in general, to testing semiconductors, and more particularly, to a novel probe that is used for forming a low resistance electrical connection to a semiconductor die.
In the past, the semiconductor industry had used burn-in to assist in improving the quality of semiconductor devices. In most cases, burn-in was limited to packaged semiconductor devices because it was difficult to perform testing of individual semiconductor die or semiconductor wafers. As semiconductor packaging costs increased and semiconductor technology produced greater levels of integration, the need to burn-in and test individual semiconductor die and semiconductor wafers increased. In most cases, burn-in of semiconductor devices was performed at temperatures of up to 130.degree. centigrade. After a period of time, typically after 24 to 48 hours, testing would be performed to detect failures that had occurred. In some cases, the testing was also performed at elevated temperatures.
One disadvantage of prior methods of testing semiconductor wafers or individual die during or after burn-in was the difficulty in forming low resistance connections. Generally, the probe pads of a semiconductor die were exposed during burn-in. Consequently, the conductor material that was used for the semiconductor's probe pad or bonding pad oxidized thereby forming an electrical barrier that prevented making low resistance contact to the semiconductor die.
Another disadvantage of prior methods for forming connections to semiconductors during burn-in was maintaining electrical connection to the semiconductor die's bonding pads. The elevated temperatures encountered during burn-in operations caused semiconductor die to expand. Since the coefficient of thermal expansion of prior contact devices did not match that of silicon, the die and the contact expanded at different rates which made it extremely difficult to maintain alignment between the semiconductor die's bonding pad and the probe or contact device.
Accordingly, it is desirable to have a contact or probe that can form a low resistance connection to the bonding pad of a semiconductor die, and that has a coefficient of thermal expansion that essentially matches that of silicon.